1. Field of the Invention
The present invention relates to a semiconductor device having local connections, more particular to a semiconductor device having local connections composed of conductive plugs filled in an insulating layer.
2. Description of the Related Art
A semiconductor device having memory cells includes a large number of contacts in the cells. There are also numerous local connections which connect between locations near each other in a memory cell.
A contact is formed by forming a contact hole in a thick interlayer insulating film and implanting impurities to both the n-type diffusion region and p-type diffusion region separately in order to adjust the resistance and by burying the contact hole with a metal to form a metal plug. When forming a local connection, it is also necessary to separately form a contact hole and implant impurities to the n-type diffusion region and p-type diffusion region. Therefore, four steps were required to implant impurities to form the metal plug and the conventional process for manufacturing such a semiconductor device suffered from increased manufacturing costs.
In this specification, note, a "local connection" means not only a connection of diffusion regions, but also connection of locations near each other in a cell such as connection of inverters.